Artificial board



Dec. 22, 1959 R. M. DORLAND ET AL ARTIFICIAL BOARD Filed July 6, 1955lil Imam/m5 2,918,398 o ARTIFICIAL BOARD Rodger Malone Dorlandand`Maxwell Menuhn Yan,

Sault Ste.` Marie, Ontario, and Elliott G. Heslop, Sturgeon]5`alls,0ntario,` Canada, assignors, by mesne as-V signments, to AbitibiCorporation, Alpena, Mich., a corporation ofDelaware .t t

` Application July `6, 195s, serial No. $20,319 Claims priority,applicationlCanada February 19, 1953 ls) claims. (c1.` 16a- 132) Thisinventionrelates to afprocess `for making artificial board and to theproduct` of such process. ,A

This application is a continuation-impart of application Serial No.362,654, filed .lune 18, `1953, now abandoned. `It is well known thatanartifcial board of-the type `known, as .hardboardgcanbe produced bytaprocess includingthe debration and refining ofitiibrous material t t`such as wood` chips, followed by forming and dewatering Vof the wet lapon a Fourdrinier machine and consolida-.

`tion under heat and pressure toprovide a `hard compact fibrousmassbound together bythe hemicellu1oses,tlignins and othernaturalfbinding,constituents-of.the`wood. vIf

desired, additional ingredients can be added, such as sizes, forexample, various waxes,land additional binding mate- Arials such assynthetic resins, for example, phenol- `formaldehyde resin. Y

A board produced in the foregoingmanner has certain disadvantages inrelation to modern demands. The bers cause minute pits inthe surface,thus increasinglthe number ofcoats ofpaintrequired to achievea good`paint surface. In addition, the smooth surface of the'board has va darkappearance andis `frequently marked withdense kspotswhich` makes `it`ditiicult to achieve a blond Vfinish. ,The smooth surface of the boardrefers tothe surface :in direct contact vaithwthe vflat platens of thepressaduring ,final consolidation., The Arough surface is.,mprinted.with supporting wire screen `during the` consolidation.` For `zmostpurposes the` surface appearance faceonly isV of importance.` i t, n Therequirement for an improved surface hasbecome lof increased importancein recentyears.` Rising: wood ,.costsand changing economics have maderitnecessary to usea `higher.proportionlofwaste wood-than formerly, :moreof `the`brasher` and `lesssuitable-species` and even .,bark, 'and,have*made `it essential to increase machine speedstand therefore-,the vratcofwater removal to;as Ahigh a point as possible. Coarser fibers of freerdrainage of this smoothsurr 2,918,398 `Parented Dec. 22, 1959 ,wetlap.The top layerof better liber covers the poor fberstand bark specks andgives a board ofimproved appearance and surface qualities. VThis overlayprocess has serious limitations because the addition of relativelyflarrgew,volumes` o f wateris necessary to make the secondary overlaystock flow and form properly. The water is difficult to remove, "Specialequipment is needed to provide the slush stock. Also the secondary stocktends to ,fill fvalleysjin the underlying surface and w away from thepeaks so that it is necessary to use a substantial .thickness of overlayto'give the desired evenness of surface. This `is costly. o o t t Yetanother `solution which has previously been adopted is to laminate athin board with good surface qualities to a consolidated base sheetformed from coarser bers. A sheet` of paperican beused as the surfacelaminate. This procedure has the disadvantage that a large amount Vofadhesive is necessary to give a goodbond between the base sheet and thesurface sheet. `Even with a large amount of adhesive the `surface sheetmay scale away under somel conditionse. 'Alsoa considerable quantity ofadditional equipment will be needed to" make a laminate lwhichwill infact have an even surface. Inaccrdance with the present invention it isproposed 25 .tapply a sheet of paper to'the upper surface of the wet lapafter `a large vproportion of `the w'ater has been removed from thewetlap but before the latter has been consolidated It hasbeen found thatthis produces an `irlterlocling of `the fibers -of theip'aper and of thewet lap and a bc'niiling` between the paper and. the wet lap due to thelignin's, Lhenicclluloses and other natural binding constituents 'of thepul`p Thus' thereis produced a board which has' the"gr`eatly`impr'ovedsurface qualities due to rthe fine `fibers lof` the paper, in whichthere is an integral bondi'gbetween the paper and the underlying coarserfibers'andwhich isof low cost as a thin surface layer is .used andaslittlemodiiication kof the basic process is necessary. M lf f f A drysheet of paper shouldibe used to give increased absorbency to thebindingconstituents of the wet lap.

o Additional strengthening of the `bond between the paper andthe'underlying masscan' bei'o'btained bythe use of a thin layer of'additional binder, although this invention considered in its broadestaspect isnot limited to the inclusinof such a binder; The binder tendsto give a 'r'rioreunifor'm bonding b y` filling in and providing a bondv;therevalleys` occurfiin the base sheet. o Y

Particularly good results have `been obtained by using t "ardrying oilas abinder. Itfhas been found that,. in addihave been usedto,conform-,with the increasedmachine fspeeds andto ,offset the decreaseindrainage` rates pro- .luced by bark particles. Bark, particles alsoresult ina darkcrsurface.` f Thus a demand for an improved surface ,has,actually` coincided with -a deterioration `in surface lappeafallc- ,t :y.int yQne approach to, enhancing thesurface` appearanceu of `the smoothsurJface; of theboard ewould'be touiseiner l fyyhic'h'ase'cohdary headbqx `l`y`` of specially prepared liuc fibers in a water suspension ontothe partially f'rr'x'l'd ,1 HQWsYeft; this wuld, :Substantially increase:the s vtion tofthe contribution Vofthe drying oil to the bonding Vo'f"the paper sheet todthe `base `mat, the drying oil gives surfaceproperties comparable to those of the treated board`prc' duced`bydipping or roller application of a drying `oil"to thc surface of theboard, but with the` expendiftueofta farsmaller amount ofdryinfgoil.Part of the dryingoilalso gives ariwatfer resistant screen adjacent to`the surface of the paper to prevent the formation of water 'spots'whichfmight othervi/'ise be formed` during thehot lpressingsteptj Thesewat'erspotsare'believed to be due `torliquid water and-thesolublestherein being forced to vthe "surfacefnd the water liashingintosteamon-contact `withthe lhot platen. "The water solublesugars-and othersubstances cause discolouration.` It has also been found thatlthe oilsgive a pleasant translucent appearance to the surface of the board, butthat in spite of this translu- Vcency dense" spots on the surface of thebase sheet are hidden. t

The sheet of paper used as an overlay in accordance with44thifsinvention may vary widely in grade, thickness andother qualities..Preferably a low` cost paper of good absorbency such as news print isused.` Other suitable papers include sulphite, sulphate and neutralV`siilphite ywill have alreadytaken place.

semi-'chemical sheets. The weight of the standard newsprint sheet whichis preferred is about 11 lbs./ 1000 sq. ft.

The binder can be a drying oil such as linseed oil or a compositionconsisting of a blend of drying oils with petroleum polymers. Otherdrying oils in addition `to linseed oil include soybean oil, tall oiland tung oil. Alternatively many other binders may be used includingsuitable formulations of synthetic resins such as phenolic resins,urea-formaldehyde resins and vinyl resins. Rubber latices such asbutadiene-styrene latex and animal or vegetable glue or other bindersalso may be used. Ideally the binder should be cheap and effective insmall amounts and should give a bond resistant to water, weather andheat. The binder should not stain the overlay. The quantity to be usedwill vary with thenature of the binder and other factors but in generala considerably lesser amount Will bev used than in the case of anordinary laminate as the binder is not used as the primary bonding agentbut only as an adjunct to the bonding obtained by the interlocking offibers and use of the natural binding constituents of the base stockobtained in accordance with this invention. 11/2 lbs. of solids/ 1000sq. ft. of board is the recommended quantity in the case of linseed oil.The quantity used will generally be within the range` of 1 to 5 lbs.,but could be within the range of 0.5 to l0 lbs. The use of more than 2lbs. does not significantly improve lthe adhesion of the paper to thebase sheet, but more than 2 lbs. may be added to give a tougher surface.v1?/2 lbs. of phenolic resins and butadiene-styrene latex have alsoproved effective. Appropriate modifying agents, catalysts and driers maybe added to the binder. Thus in the case of some drying oils, it may bedesirable to add a drier such as a naphthenate of manganese, cobalt,lead or iron. In the case of linseed oil it has been found that wherethe oil is added prior to'consolidation the heat during pressing andsubsequent ,baking sutiiciently hardens the oil.

The wet'v lap shoul'd'be fdewate'red to a consistency of 60 to 75%moisture content or aboutl solids before the sheet of paper is applied.To reach this consistency the water is reduced first by free drainagethrough the wires of the Fourdrinier machine, followed by suctionYdrainage and the application of cold pressure rolls. The wet lapemerging from the pressure rolls will have a smooth surface whichfacilitates the bonding of the overlay sheet of paper. at this stage. Inaddition, most of the dewatering The overlay will therefore interfere.to la minimumextent with the dewatering of the pulp. The overlaysheetcan be applied by rollers subsequent toV the cold pressure rolling andprior tojcorisolidation in the hotI press. `Where abinder .is to'be usedit can be coated on the surface of the paper which willbe in 4contactwith the wetlapprior to the applicationV of thepaper to the wet lapj. inthe case of binders such as linseed oil and other drying oils it hasbeen found that i the binder can alternatively be applied to theouterl'surface of the paper after'consolidation in thefhot press. Thedrying out in the hot press will makefther paper suf-- ficientlyabsorbent for-the binder t0 penetrate the paper overlay andthe'4 surfaceof the lbase sheet. ,When the board is baked the binder willfform a bondbetween the paperv and the -basel sheet. It is,lhowever, preferred that'the binder be applied priorl toy consolidation undefrhe'at and pressuresince va partaof the binder then formsa water resistant barrier toinhibit the formation of water spots."

In the drawings which illustrate the Vpreferred'embodiment lof thisinvention: 4

Figure lis a diagrammatic,'illustration of arnanner of Y carrying outthe process of this invention.

Figure 2 is a vertical sectional View of aboard produced by theprocessofthis invention. y r

The,V preferred embodiment o f this invention will be illustratedwithreference tothe production of l." hardboard with a newsprint overlay andusing a linseed oil binder. Y

A furnish consisting of mixed hardwoods and softwoods in approximatelyequal proportions is providedby separate treatments of Wood chips indeiibrators A1 and A2 respectively and secondary refiners B1 and B2 andis passed into storage chests C1 andCz. with steam prior to and duringthe defibrator step. lThe consistency of the pulp entering the storagechests is about .4l/2%, by weight solids. The hardwood and softwoodpulpsare combined in approximately equal amounts in mixing chest D wherethe consistency is adjusted to about 3%. Here suitable sizing materialssuch as a wax emulsion are added. The pulp is transferred through pipe Eby pump F .to headbox G from whence it is fed onto the Wire screen ofthe Fourdrinier H. At this stagey the wet lap is about 3 thick. Part ofthe water is eliminated by free drainage in section I and further Wateris removed by one or more suction boxes K and one or more sets ofsuction rollers L. The wet lap is then passed through one or more pairsof cold pressure rollers M. Preferably several such pairs of rollers areused with a nip pressure vaying fromlbs. per linear inch to 750 lbs. perlinear inch. The wet lap sheet emerges about to l thick .and with amoisture content of about 65 and is translwith the paper overlay isconsolidated under heat and pressure in'hot press S where it issubjected to pressure `varying between 50 and 650 p.s.i. at temperaturesof about 390" F. during a pressing cycle of about 8 minutes total cycle.From thence the board is passed to baking oven T where it is treated atto 165 C. for about 3 hours or longer, after which it is humidiiied toabout 7% moisture. i

,As illustrated'in Figure 2 the product is a basefsheet consistingl of aconsolidated fibrous mass vU integrally bonded to overlay sheet V alonglineW. There is an interlocking of fibers along line W which gives afirm bond. In addition, there is the combined bonding effect of thenatural binders from the pulp and the drying oil. Partof the drying oilwill be adjacentto line W and 'will be available for bonding. Part ofthe drying oil will be forced outwardly by the migration of bindingconstituents and moisture fromthe Wet lap to form a water resistantbarrier shown as X. For the purpose of illustration barrier X is shownas being well defined. In practice it will not have clearly definedmargins.

The product shown in Figure 2 has good abrasion resistance due tol thedrying oil, a pleasing translucent appearance and superior bendingproperties giving small -v about one coatlof paint can be eliminated'bythe irn- Aproved 'surface' of the product in comparison with ordinaryhardboard.- As the coat of painting is several cents `per square footper coat and the cost of the impregnated overlay iszbnly a fraction of acentY per square foot, a considerable-(saving is achieved. The surfaceeffects Vof 'the product are comparable to that of board treated by yimmersion or roller application with between 2 and 8% of `dryingoil byweight of the board. It is apparent that the present process will bemore economical. The present processfalso compares favourably with theslush overlay process in whichl an overlay of between 25 lbs. and

100 lbs./l000sq.' ft.of board is normally used and in which, inaddition, there are higher equipment costs.

It has-beenl found that the foregoing process can be extended toprovide'an improved artificial board having Va surface printed with apattern'sucllasa simulated wood grain.v s j The wood is treated It hasbeen found that, where a pattern is printed on the sheet of paper whichis combined with the surface of the board in accordance with the processoutlined above, there is excellent resistance to defacement of thepattern by abrasion as compared with post-lamination procedures in whichpaper having a printed surface is merely adhered to a inished board.

In an experiment conducted to confirm the foregoing, three samples wereprepared, namely:

(I) A printed overlay sheet of paper combined with a 1/8 standard basein accordance with the process described in the main disclosure using alinseed oil binder in the proportion of 11/2 lbs. of binder to 1,000square feet of board.

(II) A similar printed sheet of paper to (I) glued to a finishedstandard board using ordinary paper mucilage, cold, with slightpressure.

(III) A similar printed sheet of paper to (I) glued to a nished standardboard using a latex cement, cold, with pressure to give a good bond.

Samples of each type were tested on a laboratory Taber Abraser, with thewheels of the tester being reground between each sample to provide afresh surface each time. Observations were carefully made during eachtest to determine the following end points (measured in revolutions tothe nearest as points of comparison:

(A) The point at which the pattern lines rst showed definite signs ofwearing off,

(B) The point at which the pattern lines had cornpletely disappeared,

(C) The point at which the overlay paper first showed definite signs ofbreaking through to the base board, and

(D) The point at which the overlay paper had completely worn olf,leaving the base board showing through.

The results of these tests were as follows:

It will be apparent from the results of these tests that the process ofthis invention imparts extremely elective resistance to defacement byabrasion to patterns printed on an overlay.

We claim:

1. A process for making hardboard comprising the steps of forming athick wet lap consisting essentially of coarse fibrous wood pulp andcontaining the natural lignocellulose, partially dewatering the wet lapto a solids content of 25% to 40% by weight, applying a finished sheetof paper to the surface of said partially dewatered wet lap whichcomprises the smooth surface of the iinished board, and consolidatingthe wet lap into hardboard under combined heat and pressure andsimultaneously consolidating the sheet of paper therewith.

2. A process as claimed in claim l in which said sheet of paper issubstantially dry when it: is applied.

3. A process as claimed in claim l in which said paper prior toapplication thereof to said wet lap has a pattern printed thereon on thesurface opposite the one which is applied to the wet lap.

4. The product produced by the process claimed in claim 1.

5. A process for making hardboard comprising the steps of forming athick wet lap consisting essentially of coarse fibrous wood pulp andcontaining the natural lignocellulose, partially dewatering the wet lapto a solids content of 25% to 40% by weight, applying a finished sheetof paper to the surface of said partially dewatered wet lap whichcomprises the smooth surface of the nished board, applying a layer ofbinder to a surface of said paper, and consolidating the wet lap towhich the sheet of paper and binder have been applied into hardboardunder combined heat and pressure and simultaneously consolidating thesheet of paper therewith.

6. A process as claimed in claim 5 which comprises the additional stepof curing the consolidated hardboard to strengthen the bond between thepaper and the board.

7. A process as claimed in claim 5 in which the binder is drying oilused in a quantity of about l to 5 lbs. to 1,000 sq. ft. of board.

8. A process as claimed in claim 5 in which the binder is applied to thepaper before the paper is applied to the wet lap, and that surface ofthe she-et of paper to which the binder is applied is thereafter appliedto the wet lap.

9. A process as claimed in claim 8 in which said paper prior toapplication thereof to said wet lap has a pattern printed thereon on thesurface opposite the one which is applied to the wet lap.

References Cited in the file of this patent UNITED STATES PATENTS242,253 Benton May 31, 1881 513,017 Howard Jan. 16, 1894 695,787 BrownMar. 18, 1902 793,832 Engelmann July 4, 1905 1,680,896 Marr Aug. 14,1928 1,941,536 Boehm Jan. 2, 1934 1,995,145 Frost Mar. 19, 19352,077,714 Rozema Apr. 20, 1937 2,161,655 Ellis June 6, 1939 2,167,440Mason July 25, 1939 2,348,081 Linzell May 2, 1944

1. A PROCESS FOR MAKING HARDBOARD COMPRISING THE STEPS OF FORMING ATHICK WET LAP CONSISTING ESSENTIALLY OF COARSE FIBROUS WOOD PULP ANDCONTAINING THE NATURAL LIGNOCELLULOSE, PARTIALLY DEWATERING THE WET LAPTO A SOLIDS CONTENT OF 25% TO 40% BY WEIGHT, APPLYING A FINISHED SHEETOF PAPER TO THE SURFACE OF SAID PARTIALLY DEWARTED WET LAP WHICHCOMPRISES THE SMOOTH SURFACE OF THE FINISHED BOARD, AND CONSOLIDATINGTHE WET LAP INTO HARDBOARD UNDER COMBINED HEAT AND PRESSURE ANDSIMULTANEOUSLY CONSOLIDATING THE SHEET OF PAPER THEREWITH.